Robust hybrid mode-locking operation with the bulk-like transition metal pentatelluride

Transition metal pentatellurides ZrTe5 and HfTe5 have unique physical properties, such as large thermoelectric power, anomalous resistivity peak, chiral magnetic effect, etc. Here, we report that bulk-like ZrTe5 and HfTe5 exhibit excellent non-linear optical properties with the increase of the intensity of the incident light, and can act as robust saturable absorbers for generating femtosecond fiber lasers. The fiberized saturable absorbers have been prepared by transferring the mechanically exfoliated ZrTe5 and HfTe5 onto the D-shaped fiber and show polarization-dependent nonlinear optical absorption at 1560 nm. The stable femtosecond pulses can be delivered successfully via the nonlinear absorption of the bulk-like transition metal pentatellurides and the nonlinear polarization rotation effects in the fiber laser cavity. The experimental results validate that transition metal pentatellurides can act as an excellent nonlinear optical modulator and may make inroads towards robust high-performance ultrafast photonic devices.